PARAM_ONION_MSG is sometimes null

[gwicks56]

Writing some code to fix #23, and about 10% of the time my build fails with error:
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference

At MainActivity line 229.

I believe it is possible for for the intent extra PARAM_ONION_MSG to be null under a range of different conditions, not sure how you would prefer to fix. It would be easy to check for null, but then sometimes there would be no QR code displayed.

[AreYouLoco]

#96 This seems to be the same issue